(Image Credit: NASA / JPL-Caltech / Russian Federal Space Agency)When it comes to water, Mars probably holds more than any other terrestrial body (at least as far as safely retrieving goes).
While the red planet does hold an abundance of water beneath its surface (not to mention the north and south poles), locating the ice rich regions may determine how successful a future outpost will be on the crimson world.
Fortunately it looks as if scientists may have found a way to locate areas wealthy in ice water simply by "bouncing" neutrons off of the Martian soil.
(Astrobiology Magazine) Detecting water underground does not require a magical stick. Neutrons reflecting out of the soil can indicate the presence of water or ice. A novel instrument that can detect those neutrons is planned for NASA's next rover mission to Mars. [...]Even though we can use satellites to locate ice water from space, their results are not as accurate (as according to the article their signal can only penetrate one meter below the surface).
"It is like striking a billiard ball with the cue ball," Boynton said. "If you hit it directly on center, all of the energy of the cue ball (the neutron in this case) will be transferred to the billiard ball (the hydrogen atom)."
The net result is that a neutron is stopped or slowed when colliding with hydrogen. Presumably, most of the hydrogen atoms on a planet surface will be part of a water molecule.
"Water will both thermalize (slow down) and absorb neutrons, so the reflected neutron signal will be higher in thermal (low-energy) neutrons and lower in epithermal (high-energy) neutrons," Boynton explained.
Dry soil, by contrast, will reflect more high-energy neutrons. This is because it will contain predominantly heavier atoms, which act like bowling balls that barely budge when a cue ball hits them. Neutrons striking iron or silicon atoms, rather than hydrogen atoms, will ricochet with practically the same energy that they started with.
If promising regions can be located, NASA (and others) could then send robotic landers to drill through the surface, which will make it easier for future colonists to simply collect and filter the Martian water once they arrive.
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